The present invention relates generally to tools utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides an early formation evaluation tool having formation fluid sampling capability.
It is well known that it is desirable to have the capability; of evaluating characteristics of formations intersected by a wellbore before drilling operations are completed. This type of formation evaluation is known as xe2x80x9cearlyxe2x80x9d formation evaluation by those skilled in the art. For this purpose, tools have been developed which are interconnected in drill strings, and which are capable of performing tests on formations, such as pressure drawdown and buildup tests. These tests may be performed periodically during drilling operations.
However, it would also be advantageous to be able to collect samples of fluid from formations intersected by a wellbore during a drilling operation. Furthermore, it would be desirable to be able to collect such samples in conjunction with tests performed on formations, since this would be more economical and convenient than performing the formation tests and sample collections at different times, with separate tools, or on separate trips into the wellbore. Performing a formation test and a sample collection without moving the drill string between these operations would also aid in correlating the results of these operations to a particular location in the formation.
From the foregoing, it can be seen that it would be quite desirable to provide an early formation evaluation tool with the capability of collecting formation fluid samples.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, an early formation evaluation tool is provided in which fluid samples may be conveniently collected therein.
In one aspect of the present invention, successive fluid samples are received in respective successive fluid samplers of a tool by alternately increasing and decreasing fluid pressure in a tubular string in which the tool is interconnected. The fluid samples may be received in the samplers either without repositioning the tool in the wellbore, or with the tool being repositioned in the wellbore between sample collections.
In another aspect of the present invention, fluid pressure in the tubular string may also be utilized to sealingly engage one or more packers of the tool with a wellbore. The fluid pressure used to operate the packers may be maintained in the tool while the fluid pressure in the tubular string is altered to operate the samplers.
In yet another aspect of the present invention, the tubular string to which fluid pressure is applied to collect fluid samples in the tool may also be manipulated to pump fluid from a formation into the tool. Thus, various operations of the tool may be conveniently and separately accomplished as desired by merely manipulating or applying fluid pressure to the tubular string.
In still another aspect of the present invention, the tool may include a ratchet mechanism responsive to fluid pressure applied to the tubular string. In one embodiment described herein, a J-slot is used to incrementally displace a piercing member relative to a series of pressure barriers. Fluid pressure applied to the tubular string may also be utilized to cause the member to pierce one of the barriers with which the member is aligned.
In a further aspect of the present invention, the tool includes at least one fluid sampler including an actuator. The actuator is placed in fluid communication with one fluid passage of the tool to thereby cause the sampler to receive a fluid sample therein from another fluid passage of the tool. In one embodiment described herein, the one fluid passage used to operate the actuator is placed in fluid communication with the interior of the tubular string in which the tool is interconnected.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.